King Arthur - The Role-playing Wargame

I got both this game and Fallen Champions but i'm left confused as to the difference between the two. I assumed Fallen Champions is the expansion pack, to play the original campaign should i be loading this or Fallen Champions?

is FC a competely stand alone expansion pack or does it just add units/items/events to the base game? I cannot find anyone showing any difference between the two.

The store page for Fallen Champions, says that it is a standalone expansion. If you haven't played either yet, I would get you teeth cut on the original game and the integrated expansions before this one.